In rock drilling, a drilling tool is used that is connected to a rock-drilling device via one or more drill string components. The drilling can be carried out in several ways, a common method being percussive drilling where an impulse-generating device, a striking tool, is used to generate impacts by means of an impact piston that moves forward and backward. The impact piston strikes the drill string, usually via a drill shank, in order to transfer impact pulses to the drilling tool via the drill string, and then on to the rock to deliver the energy of the shock wave. The impact piston is typically driven hydraulically or pneumatically, but can also be driven by other means, such as by electricity or some form of combustion.
In another kind of impulse-generating devices the shock wave energy is generated as pressure impulses which are transferred to the drill string from an energy storage by means of an impact element that performs only a very small motion instead of, as described above, being generated as released kinetic energy by a piston moving backwards and forwards.
An example of such a device is a device where an impact element is pre-loaded using a counter-pressure chamber, and where the energy is transferred to the drill string by means of the impact element by a sudden reduction of the pressure in the counter-pressure chamber.
Another example of such a device is a device where a working chamber is arranged in front of the impact element instead of using a counter-pressure chamber, and wherein the shock waves are generated by supplying pressure medium of high pressure in form of pressure pulses to the working chamber from an energy storage.
According to the currently known technology, such solutions generate shock waves with lower energy, and, in order to maintain the efficiency of the drilling, the lower energy in each shock wave is compensated for by the shock waves being generated at a higher frequency.
A problem with all the abovementioned impact-generating devices is that available impact energy is not fully made use of.